Left ventricular (LV) hypertrophy is an important prognostic indicator in patients with heart disease. Current techniques to quantitate LV mass, including M-mode and two-dimensional echocardiography, only allow a limited assessment of LV hypertrophy. Real-time three-dimensional echocardiography (RT3D echo) is a novel technique that provides instantaneous volumetric cardiac images. In patients with suboptimal images, intravenous contrast agents provide LV cavity opacification and improve endocardial definition. The present study aimed to determine the accuracy of LV mass measurements with contrast-enhanced RT3D echo using magnetic resonance imaging (MRI) as reference standard. To this purpose, 43 patients (age: 56+/-16 years; 26 men and 17 women) with different cardiac conditions underwent RT3D echo and multiphase breathhold cine GRE MRI examinations in random order on the same day. RT3D echo images were acquired after the peripheral intravenous injection of 0.05 ml/kg of EchoGen, a dodecafluoropentane-based ultrasound contrast agent (Sonus Pharmaceuticals). Off-line calculation of LV mass from RT3D echo images was performed using an interactive aided manual tracing method to reconstruct the endocardial and epicardial surfaces. Images were analyzed by independent observers blinded to the results of the other technique. LV mass measurements by MRI ranged from 105 to 373 g (mean+/-SD: 193+/-67). RT3D echo measurements of LV mass strongly correlated with those obtained by MRI (r=0.93; y=13.7+0.89x; SEE=22.8; p<0.0001). Mean absolute difference between measurements was 19?16 g (10+/-8% of MRI-derived LV mass). Thus, contrast-enhanced RT3D echo accurately predicts LV mass in humans. This method may therefore be useful for the quantitative assessment of LV hypertrophy in cardiac patients. - three-dimensional echocardiography; left ventricular hypertrophy; myocardium - Human Subjects